1. Field of the Invention
The present invention relates to a vehicle driving condition prediction device for predicting the lateral acceleration which will occur when passing through a curve ahead, and to a vehicle driving condition warning device for producing a warning when a predicted lateral acceleration exceeds a specified reference value. The present invention also relates to a recording medium for storing data for prediction and an operation program.
2. Description of Related Art
Well known automobile navigation systems provide route guidance for the driver of a vehicle. The navigation system is installed in an increasing number of vehicles. The navigation system stores road map data, including road shapes and monitors the position of the vehicle. Therefore, the system can recognize curves in the pathway of the vehicle. It has been proposed to optimize the vehicle speed when going into a curve using the navigation system. For example, Japanese Patent Laid-Open Publication No. 5-141979 (JP-A-05141979), teaches calculating lateral acceleration G while driving through a curve from the radius of curvature R of the curve ahead and the present vehicle speed, and comparing G to a predetermined reference value G.sub.O. If the lateral acceleration G exceeds the reference value G.sub.O, the system decides that the vehicle should be slowed down, and issues a warning.
As the driver reduces the speed in response to the warning, the vehicle speed entering the curve can be optimized, so that the vehicle can pass through the curve stably.
However, problems exist with the present warning systems. The curve warning issues even when the vehicle is travelling at a safe speed. Furthermore, a warning tends to issue unnecessarily because the driver plans to reduce the speed of the vehicle according to the driver's normal driving pattern.